1. Field of the Invention
The present invention relates generally to a thin film deposition method for a wafer, and particularly to a method for selectively growing a thin film on a wafer patterned by using a material having a low sticking coefficient relative to molecules in a reactant gas. And more particularly, the present invention relates to a selective epitaxial growth in which a predetermined thin film is only deposited onto the openings formed on the patterned wafer.
2. Description of the Prior Art
There are several conventional methods that consist of the selective epitaxial growth process using the reactant gas, including:
(1) a method including a selective etching process in which the film formed onto a patterned wafer (a thin film is formed in a some kind of pattern on a wafer on the processor the manufacture of semiconductor devices that involves some processes such as the oxidation process, the diffusion process, the resist coating process, the etching process, the thin film deposition process, etc.), is selectively removed, and consequently the epitaxial growth film is only deposited onto the openings on the patterned wafer; PA1 (2) a method in which a thin film is deposited by decreasing the flow rate of the reactant gas to be supplied; and PA1 (3) the method in which a thin film is deposited by dropping the temperature of a wafer. PA1 (i) to maintain the pressure within the vacuum chamber or vessel within a lower pressure range in which the reactant gas will cause substantially no vapor phase reaction, and PA1 (ii) to maintain the surface molecular concentration of the reactant gas upon a thin film made of the material with the lower sticking coefficient below the one which would cause a nucleus formation.
One of the methods listed above, i.e., the method (1), requires that the temperature of a wafer should be raised to a higher temperature during the selective etching process.
For example, when a silicon (Si) film is selectively grown on a silicon (Si) substrate, a reactant gas that is mixed with some gases (such as SiCl.sub.2 H.sub.2 or HCL+SiH.sub.4) is used so that the selective etching process can proceed for the Si film. That is, according to the method (1), the Si film is grown on the Si substrate while the etching process is going on for the polycrystalline silicon film being formed on the oxide layer. The etching process for the polycrystalline silicon film according to that method can only proceed when the temperature of the Si substrate is higher.
Yew et al. (J. Appl. Phys. 65 (6), 15 Mar. 1989, pp. 2500-2507, "Selective silicon epitaxial growth at 800.degree. C. by ultralow-pressure chemical vapor deposition using SiH.sub.4 and SiH.sub.4 /H.sub.2 ") reports that the required temperature of a wafer is about 800.degree. C.
For this reason, the structure formed by the thermal diffusion process within a wafer might be destroyed at the high temperature.
The method (3) in which the temperature of the wafer is dropped is reported by Hirayama et al. (Appl. Phys. Lett. 52 (26), 27 Jun. 1988, pp. 2242-2243, "Selective growth condition in dislane gas source silicon molecular beam epitaxy"). This research report says that in order to accomplish the selective growth by dropping the temperature of the wafer, it is necessary to limit the flow rate of the reactant gas. In this case, however, the high-speed selective growth is practically impossible, and it can not be applied to the manufacture of the semiconductor devices.